Technical Field
The present invention relates to a liquid jet head, a method of manufacturing a liquid jet head, and a liquid jet device that injects droplets to a recording medium to carry out recording.
Related Art
In recent years, liquid jet heads in an inkjet system, which discharge ink droplets to a recording sheet or the like to record letters and figures, or discharge a liquid material to a surface of an element substrate to form a functional thin film, are used. In this system, an ink or a liquid such as a liquid material is supplied from a liquid tank to a channel of the liquid jet head through a supply pipe, and pressure is applied to the liquid in the channel and the liquid is discharged through a nozzle communicating into the channel as droplets. In discharging the droplets, the liquid jet head or a recording medium is moved, and the letters and figures are recorded, or the functional thin film or a three-dimensional structure in a predetermined shape is formed.
For example, JP 10-244668 A describes this sort of a method of manufacturing a liquid jet head. In a first manufacturing method, first, an ink passage made of a plurality of grooves is formed in a surface of a piezoelectric substrate. Next, an electrode is formed on inner surfaces of the grooves and an upper end surface of a partition between the grooves by an evaporation method or a plating method. Next, a photoresist film is applied to the entire surfaces of the inner surfaces of the grooves and the upper end surface of the partition. Next, the photoresist film on the upper end surface of the partition is removed by exposure development. In removing the photoresist film, the photoresist is left on an outer peripheral portion of the upper end surface of the partition. Next, the electrode is etched, and the electrode exposed on the upper end surface of the partition is removed. Then, a glass cover is installed on the upper end surface of the partition, and a nozzle plate is installed on a side surface of the piezoelectric substrate to which the grooves are open, whereby a liquid jet head is completed.
In a second manufacturing method, first, a photoresist film is applied to a surface of a piezoelectric substrate. Next, an ink passage made of a plurality of grooves is formed in a surface of the piezoelectric substrate. Next, the photoresist film on the upper end surface of the partition is removed by exposure development. In removing the photoresist film, the photoresist film is left on an outer peripheral portion of the upper end surface of the partition. Next, an electrode is formed on inner surfaces of the grooves and the upper end surface of the partition. Next, the photoresist film is removed, and the electrode deposited on an upper surface of the photoresist film by a lift-off method. Next, a glass cover is installed on the upper end surface of the partition, and a nozzle plate is installed on a side surface of the piezoelectric substrate to which the grooves are open, whereby a liquid jet head is completed.
JP 10-244677 A describes a method of manufacturing a liquid jet head, for forming an electrode on a side surface of a partition by an electroless plating method. First, a photoresist film is formed on an upper surface of a piezoelectric substrate. Next, a plurality of grooves is formed in a surface of the piezoelectric substrate. A partition is formed between the groove and the groove. Next, a sensitizing-activation step is carried out as pretreatment of electroless plating. First, Sn is absorbed by inner surfaces of the grooves (side surfaces of the partition) and a surface of the photoresist film. Next, the piezoelectric substrate on which Sn is absorbed is immersed in a liquid containing silver nitrate and Sn is replaced with Ag. Next, the piezoelectric substrate is immersed in a solution containing palladium chloride, and Ag is replaced with Pd. Next, the photoresist film is removed from the upper surface of the piezoelectric substrate. Next, an electrode is formed on the surface of the substrate on which Pd is absorbed as a catalyst core by an electroless plating method. The catalyst core does not exist on the surface of the piezoelectric substrate (the upper end surface of the partition) and thus a plated layer is not formed, and the catalyst core exists on the inner surfaces of the grooves (the side surfaces of the partition) and thus the plated layer is formed.
JP 2012-35607 A describes a structure of a principal portion of a liquid jet head. The principal portion of the liquid jet head includes an insulating substrate, partitions made of a piezoelectric member and arranged on the insulating substrate across an ink pressure chamber, and a nozzle plate including a nozzle hole facing the ink pressure chamber and glued to an upper end surface of the partition through an adhesive. A corner portion of the partition between a side surface on a side of the ink pressure chamber and the upper end surface to which the nozzle plate is glued is chamfered into a recessed shape. To be specific, a surface of the insulating substrate and the side surface of the partition are approximately perpendicular to each other, and a chamfered portion of the partition, that is, the corner portion that connects the side surface and the upper end surface of the partition is chamfered into the recessed shape. Next, an electrode is formed on the entire surface of an exposed surface of the partition. Next, the electrode on the upper end surface of the partition is removed.
Next, the nozzle plate is glued to the upper end surface of the partition through an adhesive. In this way, a recessed portion is formed in the corner portion between the side surface and the upper end surface of the partition, and the adhesive overflowing from between the upper end surface and the nozzle plate is accommodated in the recessed portion, so that the adhesive is prevented from flowing into the nozzle plate.
In the first manufacturing method described in JP 10-244668 A, the electrode is formed on the inner surfaces of the grooves of the piezoelectric substrate and the upper end surface of the partition between the groove and the groove, and next, the photoresist film is applied. That is, the photoresist film is applied to the surface on which the partition is arrayed and having a large unevenness difference, and thus a film thickness of the photoresist film becomes ununiform, and the photoresist film on the upper end surface of the partition cannot be highly accurately patterned. As a result, an electrode pattern with a uniform width cannot be formed on the outer peripheral portion of the upper end surface, and poor pattern such as the electrode being removed up to the side surface of the partition is more likely to occur. Further, in the second manufacturing method, the electrode is formed on the upper end surface of the partition, and the patterning is carried out by the lift-off method. Therefore, burr is more likely to occur in an edge portion of the electrode, and the burr is separated in an assembly step and becomes a cause to decrease a manufacturing yield.
Further, in the method described in JP 10-244677 A, the electrode pattern is formed in the corner portion between the side surface and the upper end surface of the partition. Therefore, the electrode in the corner portion is easily lacked or comes off, and becomes a cause to decrease the manufacturing yield. Further, the catalyst core is absorbed by the surface of the piezoelectric substrate on which the photoresist film is formed. However, the photoresist film has a water-repellent property, and thus repels the palladium chloride solution, and transfer of a fine pattern on the photoresist film to the pattern of the catalyst core is difficult. In addition, the piezoelectric substrate to which the photoresist film adheres is immersed in the palladium chloride solution, and thus deterioration of the palladium chloride solution is fast, and solution management is difficult.
In the partition made of a piezoelectric body described in JP 2012-35607 A, the corner portion between the upper end surface on the nozzle plate side and the side surface on the ink pressure chamber side is chamfered into the recessed shape. The electrode is formed on the entire exposed surface of the partition, and next, the electrode on the upper end surface of the partition is removed by a technique such as polishing or laser irradiation. Therefore, an angular electrode is exposed to an upper end of the recessed portion, and is lacked in the middle of the assembly step, and becomes a cause to decrease the manufacturing yield.